Roller leveler



April 1962 R. MUDDIMAN 3,031,009

ROLLER LEVELER Filed Dec. 15, 1958 INVE/V TOR EA/FLL R. MUDD/MA/V A/torney United. States Patent 3,031,009 ROLLER LEVELER Earll R. Muddiman, Middletown Township, Bucks County, Pa., assignor to United States Steel Corporation, a corporation of New Jersey Filed Dec. 15, 1958, Ser. No. 780,400 1 Claim. (Cl. 153104) The present invention relates generally to apparatus for straightening flat metal products and more particularly to an improved roller leveler for flattening metal strip.

Roller levelers are used extensively in modern metal working mills for flattening metal strip to remove irregularities from the strip which are the result of processing stresses. Examples of such irregularities are full centers, wavy edges, and diagonal or herringbone stresses known as bananas. Roller levelers are also used to eliminate from continuous strip, strip bow, bends, curvature, and coil set caused by coiling, bending and other processing over small diameter rolls.

Prior to my invention, the rolls at the entry end of the conventional roller leveler were adjusted to nest close together in order to deep-work the metal to iron out stress irregularities. Such deep-work resulted in curvature of the metal as it passed between the entry rolls. The amount of such curvature depended upon the thickness of the metal being worked and the diameter of the entry rolls.

The rolls at the exit end of the roller leveler were adjusted in relation to each other to provide a relatively flat discharge pass line. To accomplish this the rolls were spaced apart a distance approximately equal to the thickness of the material that was being processed.

The intermediate rolls of the roller leveler were spaced apart a distance intermediate the spacing of the entry and exit rolls so that a tapered pass through the roller leveler resulted. This tapered setting provided deep leveling at the entry end of the roller leveler which diminished as the material progressed through the roller leveler to a skin pass between the exit rolls. A primary function of the exit pass was to level the horizontal strap bends that were caused at the entry end of the roller leveler.

-In practice, although all of the rolls in prior art roller levelers were driven at the same speed, the speed of the metal strips being flattened was faster at the entry end of the roller leveler than it was at the exit end. However, since the speed of a metal strip traveling through a roller leveler must be actually constant along its length, slippage between the rolls of the leveler and the strip occurred. Such slippage resulted in speed differentials and weaving out of alignment, commonly termed hunting and tracking respectively.

There was less slippage at the entry end of the leveler due to the close proximity of rolls to each other and the deep leveling carried on at the entry end than at the exit end where the rolls were further apart and extremely shallow leveling occurred. With entry end slippage, the strip contact surface traveled slower than the entry roll surfaces while at the exit end the strip traveled faster than the exit roll surfaces.

Slippage between the strip surface and the roller leveler rolls caused loops to form along the length of the strip in the roller leveler. The loops created a series of vibrating ripples along the length of the strip traveling through the leveler. The ripples oscillated back and forth between rolls of the leveler in an erratic pattern which varied according to surface friction between the strip and the rolls, strip shape and variations in strip stiffness. This action resulted in strip speed variation (hunting), which was particularly detrimental when the strip was fed into a flying shear from a roller leveler to producecut sheets. The hunting caused the lengths of the cut sheets to vary so that many of them had to be down-graded or recut to meet commercial tolerances.

When the roller leveler was used in a processing line to work on strip under tension, this speed differential of the strip between the rollsresulted in a weaving action causing the strip to become misaligned due to transverse irregularities in strip shape and stifiness.

It is, accordingly, a primary object of my invention to eliminate hunting and tracking of strip being roller leveled by providing an improved roller leveler having rolls of progressively increasing diameter along its length from its entry end to its exit end.

This and other objects will become more apparent after referring to the following specification and attached drawings, in which:

FIGURE 1 is a side elevational view partly in section of a roller leveler according to the present invention; and

FIGURE 2 is a diagrammatic illustration of the roller leveler rolls of the invention.

Referring more particularly to the drawings reference numeral 2 designates, generally, a roller leveler including top and bottom leveling rolls R, each having roll necks 6 rotatably mounted in bearings 8 which in turn are mounted in a lower bearing block 10 and upper bearing block 12. Each roll is adapted to be driven in a conventional manner at the same speed or revolutions per minute simultaneously by conventional spindles and a multiple pinion drive (not shown). The top and bottom rolls are staggered in relation to each other so that a somewhat serpentine pass line is provided.

The lower bearing block 10 is mounted in a bottom frame 14 which is rigidly mounted on upright supports 16. The upper bearing block 12 is mounted in an upper frame 18 which in turn is adjustably mounted on lower frame 14. Threaded screw shafts 20 which operate in nuts 22 extend through each end of the frames 14 and 18 and serve to provide vertical adjustment for the upper frame relative to the lower frame. A wormgear 24 is fixed on the bottom of each screw shaft for cooperation with a worm 26 rotatable by a shaft 28 and wheel 30 for turning the shafts to raise and lower the upper frame relative to the lower frame. Each of the screw shafts 20 may be operated independently. The upper frame 18 is urged away from the bottom frame 14 by means of helical compression springs 31.

The construction just described is conventional except for the leveling rolls R which will now be described in further detail.

Based on actual operations of roller levelers used to flatten steel strip I have found that due to slippage, as explained above, speed differential of strip between the entry and exit ends of conventional roller levelers averaged approximately .3%. This percentage was fairly constant for heavy and light gauges as the deep leveling at the entry end of the roller leveler was set relatively lighter for heavier gauges which compensated for the increased thickness. To correct for the speed differential of metal strip S traveling through the roller leveler the leveling rolls of the leveler of my invention increase in diameter progressively from the entry end to the exit end by a constant increment for each roll so that the exit roll is approximately 3% larger in diameter than the entry roll.

For example, in a roller leveler for processing steel strip S in thickness ranging from .006" to .015 for tin plate, the rolls R-l through R-11 may have the following diameters.

3 Roll: Diameter, inches R-I 2.4375 R-Z 2.4382 R-3 2.4390 R-4 2.4397 R-S 2.4404 R-G 2.4412 R-7 2.4419 R8 2.4426 R-9 2.4433 R-10 2.4441 R-11 2.4448

The rolls R-l to R-11, inclusive, thus have diameters which increase progressively in increments of about .03% so that roll R-ll has a diameter approximately .3% greater than the diameter of roll R-l.

In operation, the 3% differential in speed of the strip between the entry end and the exit end of the roller leveler is eliminated by the use of leveler rolls having progressively greater diameters as described above.

If desired, the first cluster of two or three rolls including the entry roll may have the same diameter as the entry roll and the last cluster of rolls at the exit end of the leveler may have the same diameter as the exit roll, with the intermediate rolls having progressively increasing diameters between the diameters of the entry roll and the exit roll.

While one embodiment of my invention has been shown and described, it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claim.

I claim:

In a roller leveler for flattening metal strip including a frame having an entry end and an exit end, a pair of bearing blocks supported in vertically spaced relation in said frame defining a pathway for said strip extending from the entry end to the exit end of said frame, a series of pairs of bearings mounted in aligned spaced relationship in each of said bearing blocks, the pair of hearings in one bearing block being vertically offset from the pairs of bearings in the other bearing block, and power driving means adjacent said frame the improvement therewith of a leveler roll journaled in each pair of bearings and extending transversely of the pathway of said strip, said rolls respectively in the direction from said entry end toward said exit end having progressively greater diameters, the roll at said exit end being approximately .33% greater in diameter than the roll at said entry end, said rolls being connected with said driving means for rotation thereby each at the same r.p.m.

References Cited in the file of this patent UNITED STATES PATENTS 1,894,703 Pierce Jan. 17, 1933 2,060,400 Neiman NOV. 10, 1936 FOREIGN PATENTS 548,639 Great Britain Oct. 19, 1942 

